Traditional transportation modes via water, land, rail and air revolutionized the movement and growth of our current culture. However, the adverse environmental, societal and economic impacts of these traditional transportation models initiated a movement to find alternative transportation modes that take advantage of the significant improvements in transportation technology and efficiently move people and materials between locations. High speed transportation systems utilizing rails or other structural guidance components have been contemplated as a solution to existing transportation challenges while improving safety, decreasing the environmental impact of traditional transportation modes and reducing the overall time commuting between major metropolitan communities.
One type of high-speed transportation system utilizes a low-pressure environment in order to reduce drag on a vehicle at high operating speeds, thus providing the dual benefit of allowing greater speed potential and lowering the energy costs associated with overcoming drag forces. Such systems are embodied by a tubular structure in which a near vacuum exists within the tube.
Frictional forces resulting from the high operating speeds of the vehicle render conventional carrier systems, such as wheels, impractical. Air bearings and other aerodynamic structures of a vehicle have not previously been known to be utilized in ultra-high speed, ultra-low-pressure environments. Thus, there is a need for a testing environment with controlled pressure that can replicate high speed conditions.
A wind tunnel is a tool used in aerodynamic research to study the effects of air moving past solid objects. A wind tunnel consists of a tubular passage with the object under test mounted in the middle. Gas such as air is made to move past the object by a powerful fan system or other means. The test object, often called a wind tunnel model, is instrumented with one or more suitable sensors to measure aerodynamic forces, pressure distribution, or other aerodynamic-related characteristics. These machines are sometimes designed for long-duration testing or variable flow testing, but do not contemplate ultra-low pressure and high Mach scenarios.
A wind tunnel is discussed in Anyoji et al., Aerodynamic Measurements in the Mars Wind Tunnel at Tohoku University, 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 4-7 Jan. 2011, Orlando, Fla. This wind tunnel includes, inter alia, a buffer tank maintained at a pressure lower than that of a vacuum chamber, and further includes an ejector configured to inject high pressure gas in the wind tunnel test section. To operate this wind tunnel, a vacuum is first created in a vacuum chamber and buffer tank. Once the desired test pressure is reached, the vacuum chamber is sealed off, and the buffer tank is maintained at lower pressure than vacuum chamber. The ejector then uses high high pressure gas to induce flow in the test section of the tunnel. A butterfly valve is then used to control pressure buildup within the vacuum chamber by allowing air to flow into buffer chamber. One disadvantage of such a system is that a wind tunnel test can only be conducted for approximately eight seconds, because after eight seconds the buffer tank can no longer maintain the desired test section pressure in tunnel. Another disadvantage is that the wind tunnel must be shut down each time the airflow or air pressure conditions are changed. It is therefore desirable for a wind tunnel testing apparatus and method that can operate continuously and under varying airflow or air pressure conditions on the fly.